atm: use SKB_TRUESIZE() in atm_guess_pdu2truesize()

SKB_TRUESIZE() provides a better approximation of expected skb truesize.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/atmdev.h b/include/linux/atmdev.h
index 49a83ca..43ea1b2 100644
--- a/include/linux/atmdev.h
+++ b/include/linux/atmdev.h
@@ -452,7 +452,7 @@
 
 static inline int atm_guess_pdu2truesize(int size)
 {
-	return SKB_DATA_ALIGN(size) + sizeof(struct skb_shared_info);
+	return SKB_TRUESIZE(size);
 }